= Holding force on a contracting nozzle
{title2=$F=\rho Q^2(A_0/A_1-1)^2/(2A_0)$}
For steady ideal flow through a horizontal contracting nozzle, <Bernoulli equation> gives inlet gauge pressure $p_0=\rho Q^2(A_1^{-2}-A_0^{-2})/2$. The <integral momentum equation> gives the fluid's force on the nozzle as $p_0A_0-\rho Q^2(A_1^{-1}-A_0^{-1})$ in the outlet direction. Simplification yields the displayed nonnegative magnitude. The external holding force has equal magnitude and the opposite direction.
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